Hey all.  I joined as I'm starting a little project to get my Sister-in-law's 1973 AT3 running as a birthday gift to her.  I apologize if what I'm about to ask has been covered in the forums, but I honestly don't even know how to go about searching for an answer...

On her bike, there's a small lever just below the clutch lever that connects by cable to something on the engine head.  Pulling the lever lifts this connection, but I have NO IDEA what it does.  I got a manual and haven't been able to find anything in the manual about it.  There seems to be a bit of old oil around this area, though the bike hasn't been started or ridden in a few years.  Just wondering if someone could explain what this is.  If pictures are suggested, I can take a couple today and post them.  Thanks a bunch!

In the UK this was just a blank bolt see http://www.ebay.com/itm/Yamaha-AT3-125-2459-Cylinder-Head-/360519255448 but I have seen setups like this before (non yamaha) that just 'let the compression out' which in turn just stopped the engine (early kill switch) ... I have known other people intall a spare spark plug in place of it as it has the same thread as a spark pug http://www.ebay.co.uk/itm/151865172178?clk_rvr_id=1084552117386&rmvSB=true